mouse behavior

Question
I find myself with two pet mice.  I had the first one for about a week when I wound up with the sceond. My question has to do with behavior. When I put the second mouse in the cage, the first one starting chasing it and nipping at it.  It also started thumping it's tail. The mouse I have had longer is a male, but I'm not sure about the second one. I don't want the mouse to get hurt, so I'm wondering what this behavior is about?

Answer
Dear Stephanie,

I thoroughly understand finding oneself with mice. Actually right now I find myself with a nursing kitten (every three hours).  One doesn't always plan these things!

However, a word of caution:  You don't know the sex of the second mouse. If it is a female you will almost certainly be finding yourself with a lot more mice. In less than three weeks.

For fun mathematics on mouse proliferation, check out this post:

http://en.allexperts.com/q/Mice-3824/2008/8/1-male-3-females.htm

On the other hand if it is a male, you may find that they simply never get along.  Males usually fight and they will fight to the death.  My rule of thumb is that if there is blood, the mice must be separated.  If there is just chasing and squeaking, there is no problem. Thus when it comes to finding oneself with things, you may find yourself with two separate mouse cages.

The tail thumping is a warning.

I hope this helps.

squeaks n giggles,

Natasha